<head>
    <meta name="viewport" content="width=device-width">
    <style>
    :root {
        color-scheme: dark;
        -apple-color-filter: apple-invert-lightness();
    }
    </style>
</head>

<body>
    <div id="rich" contenteditable>Hello world</div>
    <script>
    function deselectText()
    {
        blur();
        getSelection().removeAllRanges();
    }

    function selectRichText()
    {
        deselectText();
        let text = rich.childNodes[0];
        getSelection().setBaseAndExtent(text, 0, text, text.data.length);
    }
    </script>
</body>